Application of activated carbon–metal composite for fluoride removal from contaminated groundwater in India

Abstract

Fluoride contamination in groundwater is a major problem in many parts of the World. Several novel nano- and composite materials are produced and tested for removal of fluoride from water. However, not many of these techniques are applied in natural groundwater conditions that are contaminated with fluoride. Thus, in this study, the main focus is to study systematically the performance of the cerium impregnated activated carbon-based novel composite for fluoride removal from the contaminated groundwater. To achieve the objective, first, several groundwater samples that are contaminated with fluoride are collected from two different states in India for detail analysis. Then, fluoride removal efficiencies by the cerium-impregnated activated carbon composite under the groundwater conditions are evaluated, and the possible factors affecting fluoride removal are identified. Pre-treatment of groundwater by adding selected acid to adjust the pH level of natural water is adopted to enhance the fluoride removal efficiency by the composite. It is found that the fluoride concentration in groundwater is strongly associated with pH value, alkalinity and sodium ions in the groundwater. Furthermore, it is also observed that fluoride removal efficiency reduces significantly under the groundwater condition. The presence of excessive amount of bicarbonate and carbonate (or alkalinity) and the high value of pH are the major factors responsible for the reduction in the sorption capacity. Acid treatment, which resulted in a reduction in pH and alkalinity of groundwater, has improved the fluoride removal efficiency by the composite significantly. However, leaching of cerium is observed in a few cases, which is likely to be dependent on the initial fluoride concentration.